Trudeau is wearing blackface and appears to be laughing and making other gestures in the video, but it is unclear where or when the video was taken.

Last night, the Canadian prime minister’s reelection campaign was jolted by the bombshell report, first published by Time magazine, which said Trudeau wore what it described as "brownface makeup" as part of a costume at an Arabian Nights-themed party at a British Columbia school where he taught at the time.

The photo appears in the 2000-2001 yearbook at the private school where Trudeau taught, West Point Grey Academy.

“I dressed up in an Aladdin costume and put make-up on. I should not have done that,” Trudeau acknowledged late Wednesday night. “I should have known better but I didn't, and I am really sorry.“

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Trudeau also admitted that he had also dressed up in such a way in high school for a talent show.

“I didn’t consider it a racist action at the time. But now I know better,” he told the media aboard his campaign plane.

The first-term prime minister is running neck-and-neck in a tough campaign, with a Canadian federal election scheduled for Oct. 21.

The incident risks damaging Trudeau's already fragile brand.

He's made fighting racism a central pillar of his politics — he's increased Canadian immigration levels, and included numerous visible minorities in his Cabinet.

The first political opponent to speak out following the story’s publication was the leader of the left-wing NDP — Jagmeet Singh, a son of immigrants from India.

“It’s troubling. It’s insulting,” Singh told reporters.

“Anytime we hear examples of brownface, or blackface, it’s making a mockery of someone for what they’ve lived and what their lived experiences are. I think he needs to answer for it.”

Trudeau‘s main election opponent called the incident “racist.”

“Like all Canadians, I was extremely shocked and disappointed when I learned of the lack of judgment and integrity from someone who’s not fit to govern this country,” said Conservative Leader Andrew Scheer.

Canadians of South Asian descent make up about 4 percent of the nation’s 37 million population. They hold enormous sway in key election districts, known as ridings, in the Toronto and Vancouver areas.

Green Party leader Elizabeth May said she was shocked by the initial reports.

“It’s shameful. When I look at it — and it’s rare for me — I’m almost speechless,” she said before Trudeau spoke to reporters. “It demonstrates an enormous lack of judgment.“

Other prominent politicians in the U.S., particularly Virginia Gov. Ralph Northam, have come under attack after pictures of them in racist costumes have surfaced. Northam refused to resign earlier this year after he admitted he had donned blackface in the past.

Trudeau, the son of a former prime minister, may be highly regarded on the international stage for his diplomacy, but in Canada, he has come under close scrutiny for several issues. His opponents have particularly seized on a case in which Trudeau and several senior members of his government pressed a former attorney general to drop corruption charges against an engineering company, SNC-Lavalin.

He was also widely mocked for a weeklong trip to India, where he posed for photo-ops with his family in elaborate Indian outfits.